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<head><meta charset="utf-8"><title>Summary of RFC delta regarding constructability and privacy? · project-safe-transmute · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/216762-project-safe-transmute/index.html">project-safe-transmute</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/216762-project-safe-transmute/topic/Summary.20of.20RFC.20delta.20regarding.20constructability.20and.20privacy.3F.html">Summary of RFC delta regarding constructability and privacy?</a></h3>

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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/216762-project-safe-transmute/topic/Summary%20of%20RFC%20delta%20regarding%20constructability%20and%20privacy%3F/near/210788814" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Josh Triplett <a href="https://rust-lang.github.io/zulip_archive/stream/216762-project-safe-transmute/topic/Summary.20of.20RFC.20delta.20regarding.20constructability.20and.20privacy.3F.html#210788814">(Sep 21 2020 at 19:30)</a>:</h4>
<p>Is there a summary post explaining the delta for the recent major RFC change to address constructability and privacy?</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/216762-project-safe-transmute/topic/Summary%20of%20RFC%20delta%20regarding%20constructability%20and%20privacy%3F/near/210788834" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Josh Triplett <a href="https://rust-lang.github.io/zulip_archive/stream/216762-project-safe-transmute/topic/Summary.20of.20RFC.20delta.20regarding.20constructability.20and.20privacy.3F.html#210788834">(Sep 21 2020 at 19:31)</a>:</h4>
<p>If there has been and I've missed it, my apologies.</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/216762-project-safe-transmute/topic/Summary%20of%20RFC%20delta%20regarding%20constructability%20and%20privacy%3F/near/210794739" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Wrenn <a href="https://rust-lang.github.io/zulip_archive/stream/216762-project-safe-transmute/topic/Summary.20of.20RFC.20delta.20regarding.20constructability.20and.20privacy.3F.html#210794739">(Sep 21 2020 at 20:22)</a>:</h4>
<p>Sorta. Ahead of the edits, I wrote <a href="https://github.com/rust-lang/rfcs/pull/2981#discussion_r487319138">this</a>, and after the edits, I wrote <a href="https://github.com/rust-lang/rfcs/pull/2981#discussion_r487465195">this</a> (very) brief summary.</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/216762-project-safe-transmute/topic/Summary%20of%20RFC%20delta%20regarding%20constructability%20and%20privacy%3F/near/210799814" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Josh Triplett <a href="https://rust-lang.github.io/zulip_archive/stream/216762-project-safe-transmute/topic/Summary.20of.20RFC.20delta.20regarding.20constructability.20and.20privacy.3F.html#210799814">(Sep 21 2020 at 21:05)</a>:</h4>
<p>Thanks!</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/216762-project-safe-transmute/topic/Summary%20of%20RFC%20delta%20regarding%20constructability%20and%20privacy%3F/near/210799817" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Josh Triplett <a href="https://rust-lang.github.io/zulip_archive/stream/216762-project-safe-transmute/topic/Summary.20of.20RFC.20delta.20regarding.20constructability.20and.20privacy.3F.html#210799817">(Sep 21 2020 at 21:05)</a>:</h4>
<p>Just posted a question: <a href="https://github.com/rust-lang/rfcs/pull/2981#issuecomment-696376164">https://github.com/rust-lang/rfcs/pull/2981#issuecomment-696376164</a></p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/216762-project-safe-transmute/topic/Summary%20of%20RFC%20delta%20regarding%20constructability%20and%20privacy%3F/near/211233243" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> rylev <a href="https://rust-lang.github.io/zulip_archive/stream/216762-project-safe-transmute/topic/Summary.20of.20RFC.20delta.20regarding.20constructability.20and.20privacy.3F.html#211233243">(Sep 25 2020 at 09:00)</a>:</h4>
<p>Just as a general note, I feel more comfortable with this design than the previous though I'm not sure if the <code>Here!()</code> macro and related "Scope" types are a bit too far out there. In general, has this update been better received than the previous mechanisms? Do we have next steps?</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/216762-project-safe-transmute/topic/Summary%20of%20RFC%20delta%20regarding%20constructability%20and%20privacy%3F/near/211806845" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jack Wrenn <a href="https://rust-lang.github.io/zulip_archive/stream/216762-project-safe-transmute/topic/Summary.20of.20RFC.20delta.20regarding.20constructability.20and.20privacy.3F.html#211806845">(Sep 30 2020 at 19:14)</a>:</h4>
<blockquote>
<p>In general, has this update been better received than the previous mechanisms?</p>
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<p>Yes, I think so. The <code>Here!()</code> mechanism eliminates the hand-waving that <span class="user-mention" data-user-id="117495">@rpjohnst</span> was <a href="#narrow/stream/216762-project-safe-transmute/topic/Stability.20and.20visibility/near/209573531">concerned</a> about. The new <code>transmute!()</code> hides this implementation detail (and others), such that the initial stable surface of the RFC can be very small; I think this assuaged some concerns of <span class="user-mention" data-user-id="204346">@Ashley Mannix</span>. However, I'm concerned that we're still fairly lacking in feedback from the relevant teams.</p>
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<p>Do we have next steps?</p>
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<ol>
<li>I've been working on building a reference model of the RFC's transmutability rules in Rust. <strong>I could <em>really</em> use some help with it.</strong> An executable model will help make the RFC's prose more precise, and massively aid with implementation.</li>
<li>I have a few minor edits to make to the RFC, including the addition of the lint addressing <span class="user-mention" data-user-id="125294">@Aaron Hill</span>'s <a href="https://github.com/rust-lang/rfcs/pull/2981#discussion_r481410864">concerns</a> about size-adjusting transmutations.</li>
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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/216762-project-safe-transmute/topic/Summary%20of%20RFC%20delta%20regarding%20constructability%20and%20privacy%3F/near/211886427" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> rylev <a href="https://rust-lang.github.io/zulip_archive/stream/216762-project-safe-transmute/topic/Summary.20of.20RFC.20delta.20regarding.20constructability.20and.20privacy.3F.html#211886427">(Oct 01 2020 at 09:27)</a>:</h4>
<p>Posted <a href="https://github.com/rust-lang/lang-team/issues/21#issuecomment-702010095">an update</a> to the lang team's GitHub. Hopefully this gets discussed at the next meeting, and we'll hear about next steps we should take.</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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